1. Field of the Invention
The present invention relates to an apparatus and method of transmitting a preamble having additional information in differential modulation packet data communication. More particularly, the present invention relates to an apparatus and method of transmitting a preamble having additional information in differential modulation packet data communication, in which the preamble is phase-rotated so as to correspond to the additional information and detected, thereby determining the information added to a packet.
2. Description of Related Art
In digital data communication, a packet data communication method is generally used, in which long length data is divided into data having a predetermined length, information necessary for data exchange is added to the divided data to form packet data, and the packet data is transmitted.
The packet is converted into symbol streams to then be transmitted through physical channels. The symbol streams transmitted through physical channels are largely divided into a preamble symbol stream and a packet data symbol stream. The preamble symbol stream is a predetermined symbol stream to be transmitted to a receiver to be used for synchronization information extraction and channel distortion compensation to allow the receiver to receive proper data. The packet data symbol stream is a symbol stream transmitted from a transmission apparatus 10 after mapping packet data including a packet header and a payload into a transmitted symbol.
The packet header is a part of transmitting data including additional data concerning use of a packet to be transmitted, information for transmitting data to a correct destination, and network controlling, etc. The packet payload is a part of transmitting data including actually transmitted information in a packet.
Differential modulation is used to transmit data in a physical layer in digital communication. In the differential modulation, an n-th transmitted symbol is determined by performing an operation on an (n−1)-th symbol and a symbol corresponding to n-th digital data to be currently transmitted. That is to say, in the differential modulation, the information in the n-th transmitted symbol is transmitted along with a difference between the n-th symbol and the (n−1)-th symbol. General differential modulation techniques include differential phase shift keying (DPSK) modulation, and [pi]/4 differential quadrature phase shift keying ([π]/4-DQPSK) modulation. In the general differential modulation, it is not necessary for a receiver to restore a reference phase of a received signal, thereby simplifying a configuration of the receiver.
However, in the conventional differential modulation based packet data communication, a preamble is simply used in transmitting a predetermined symbol stream to be used for synchronization information extraction and channel distortion compensation.